1. Field of the Invention
This invention relates to hepatitis B core antigen (HB.sub.c Ag) and, more particularly, to a process for preparing hepatitis B core antigen in high yield and purity.
Hepatitis B is one of the types of viral hepatitis which results in a systemic infection with the principal pathologic changes occurring in the liver. This disease affects mainly adults and is maintained chiefly by transfer of infection from long term carriers of the virus. Usual methods of spread are by blood transfusion, contaminated needles and syringes, through skin breached by cuts or scratches, by unsterilized dental instruments as well as by saliva, veneral contact or exposure to aerosolized infected blood.
The incubation period of type B hepatitis is relatively long: from 6 weeks to 6 months may elapse between infection and the onset of clinical symptoms. The illness usually beings with fatigue and anorexia, sometimes accompanied by myalgia and abdominal discomfort. Later jaundice, dark urine, light stools and tender hepatomegaly may appear. In some cases, the onset may be rapid, with appearance of jaundice early in association with fever, chills, and leukocytosis. In other cases jaundice may never be recognized and the patient may be aware of a "flu-like" illness. It is estimated that the majority of hepatitis infections result in a mild, anicteric illness.
Serum obtained from patients with hepatitis B infections usually contains three distinct morphologic forms. The largest of these morphologic forms, a 42-nm to 45-nm double shelled spherical particle, often referred to as the Dane particle (HBV), is believed to be the virus of hepatitis B. The outer surface or envelope of the Dane particle (HB.sub.s Ag) surrounds a 27-nm inner core which does not react with antibody against HB.sub.s Ag and which contains a distinct antigen, the core antigen (HB.sub.c Ag). Antibody to HB.sub.c Ag appears after acute hepatitis B infection, and also can be demonstrated consistently in chronic carriers of HB.sub.s Ag. Highly sensitive techniques are not available for detection of the HB.sub.c Ag system. A deterrent to the more widespread use of such techniques, however, is the absence of a simple yet practical and effective method for obtaining HB.sub.c Ag. The methods proposed heretofore generally involve the use of selected plasma which contains exceptionally high amounts of Dane particles.
2. Objects of the Invention
It is, accordingly, an object of the present invention to provide a practical and effective method for obtaining HB.sub.c Ag. Another object is to provide an improved method for concentrating and purifying HB.sub.c Ag. Still another object is to provide a method for obtaining HB.sub.c Ag from biological fluid found positive for HB.sub.s Ag rather than from selected high titer HB.sub.s Ag plasma. A further object is to provide immunogenic and therapeutic compositions containing HB.sub.c Ag. These and other objects of the present invention will be apparent from the following description.